Effective Tricationic Surfactants that Prevent Oxidation of Iron Atoms on the Metal Surface in Acidic Environment

One of the methods that can avoid the rapid corrosion of the metal surface, which occurs when iron atoms on steel surface are oxidized in an acidic environment, is to use suitable inhibitors. From this point of view, in this study, 4 tricationic surfactants containing long chains of 14 to 16 carbons at the end of the compound and 6 to 11 carbons in the middle of the compound were synthesized. The FT-IR and NMR spectra confirmed the chemical formulas of these surfactants. The surfactants’ physicochemical parameters (critical micelle concentrations, surface tensions at these concentrations and Gibbs free energies of micelle formation) were determined. Then, their effectiveness against the corrosion of the metal surface by iron atoms’ oxidation in 1.0 M HCl solution was measured by gravimetric method. For this purpose, metal coupons were immersed in acid solutions with and without inhibitors for twenty-four hours at room temperature. Very good inhibition efficiencies (around 95–97%) were obtained for different inhibitor concentrations (1, 5, 10, 25, 50, 100, 250 ppm) in the rust tests. The equilibrium constants (K_ads) and Gibbs free energies (ΔG_ads) of their adsorption on the metal surface, which are the reason for these strong inhibition activities, were calculated by Langmuir Isotherm studies. To support their anticorrosion activity, the metal surfaces’ contact angles and scanning electron microscopy images with 1000 times magnification were obtained.